When observing a sample by using a microscope, the visual field that can be observed at one time is mainly determined by the magnifying power of an objective lens. As the magnifying power of the objective lens increases, the sample can be observed more finely, but the observation range becomes smaller.
For the purpose of, for example, preventing an observation site of the sample from being overlooked, it is demanded that the entire image of the sample and the currently-observed visual field range be ascertained simultaneously. A known microscope system, that is, a so-called virtual slide system, is equipped with an electrically-driven stage or an encoder-equipped stage and generates a wide-field-angle overlapped image by overlapping a plurality of still images acquired while shifting the visual field of the sample (e.g., see Patent Literature 1).
Furthermore, a known imaging system generates an overlapped image by calculating the relative positional relationship between acquired images by performing image processing, such as pattern matching (e.g., see Patent Literature 2).
In such an imaging system, if the relative positional relationship, that is, the stage position, is lost during the overlapping process, the stage position is searched for by calculating the relative positional relationship between the already-generated overlapped image and the newly-acquired image, and the overlapping process resumes when the search is successful.